Pete Seeger was a working-class advocate who delivered the news in songs that could be sung by everyone, in four-part harmony. “I'll sing out danger, I'll sing out warning,” he sang, “I'll sing out love between my brothers and my sisters, all over this land.”

Seeger's “If I had a Hammer” is one of those songs that seems to be known by everyone. But what is it, exactly? Is it a children's song? A call to revolution? A melody handed down by word of mouth through the ages? It always seems to have been with us, but it was written only in 1949 by Seeger and his collaborator in the Weavers, Lee Hays. The song was a marvel of simplicity and directness with a melody that was instantly memorable.

It was also deemed dangerous enough to contribute to Seeger's reputation as a radical who eventually found himself blacklisted and indicted for contempt by Congress during the McCarthy era. Words like “freedom” and “peace” were seen as subversive and potentially seditious in certain quarters of the federal government, especially coming from a popular singer.

It's as good a way as any of summing up the contributions of a complicated folk musician and political activist. Seeger, who died Monday at 94 of natural causes at New York-Presbyterian Hospital, went from studying journalism in Harvard classrooms to hoboing across the country singing folk songs to anyone who wanted to hear them. He left behind a complex legacy: a beloved yet prickly figure who nonetheless openly detested many aspects of capitalism, openly embraced communism and was condemned for it, and never wavered in his belief that equality should extend not only across lines of race and religion, but of economic class and privilege.

Though countless musicians and genres adopted his tunes — he was a touchstone for the folk renaissance led by Bob Dylan in the early ‘60s, the chiming folk-rock of the Byrds later in the decade, a mentor and muse of sorts to Bruce Springsteen, who devoted an entire album and tour to Seeger's songs — the tall, lanky troubadour never shifted his gaze from the folk vernacular. With 12-string guitar and five-string banjo, he was the Johnny Appleseed of the folk tradition, spreading its songs into children's classrooms, union rallies and tony concert venues such as Carnegie Hall with a mixture of homespun conviction, humor and humility. At his shows, his audience was not treated as a bunch of passive onlookers, but as collaborators and fellow singers.

Born in 1919 in New York City, Seeger went to boarding schools and aspired to become a journalist. But music was always around him and eventually became integral to his life. His father, Charles, was a musicologist and composer; his mother, Constance, was a concert violinist. Charles Seeger was also something of an activist, with deep-seated political convictions that would shape young Pete's world view.

Pete Seeger studied banjo, and eventually found himself taking a lesson in North Carolina from the great folk musician Bascom Lamar Lunsford. He had found his calling, and dropped out of Harvard soon after. He later studied guitar with Huddie Ledbetter, aka Lead Belly. Seeger's long-necked five-string banjo became his trademark instrument, and a perfect tool for crafting melodies. He would use those melodies to rally unions and activate peace marches, especially after joining forces with Woody Guthrie, Hays and others in the Almanac Singers in 1941. They sang anti-fascist and anti-war songs, but drifted apart after Seeger was drafted by the Army and served in the Pacific War.

His experience in that bloody conflict only re-energized Seeger when he returned home, and he threw himself into the emerging labor movement with newfound vigor. A newsletter, the People's Song Bulletin, became the calling card for Seeger, Guthrie, Hays and their compatriots. For Seeger, song was more than just an entertainment. It was a means of demonstrating to people of all races and religions their common purpose, a way of breaking down differences. He reluctantly made the move into nightclubs, but there he was able to expand his audience, sharpen his arrangements and provide a foundation for a recording career.

With Hays, Ronnie Gilbert and Fred Hellerman he formed the Weavers in 1949 and they enjoyed a huge 1950 hit with a version of Lead Belly's “Good Night Irene.”

The Weavers sold millions of records during this era and scored hits with songs such as “On Top of Old Smokey” and “Kisses Sweeter than Wine.” But their success was cut short by Seeger's troubles with the government. The House Un-American Activities Committee linked three of the four Weavers to the Communist Party, and it cost the group concert bookings and television appearances. Seeger had joined the Communist Party in the ‘40s, then quit. He later said his party membership was a decision he regretted, but he continued to identify himself as a communist with a lower-case “c.” Seeger was indicted in 1957 on 10 counts of contempt of Congress and sentenced to a year in prison in 1961, but an appeals court dismissed the indictment. Right-wing groups continued to picket his concerts, though Seeger brushed it off: “The more they protested, the bigger the audiences became.”

He was right. Seeger became a beacon to many artists on the emerging folk scene of the ‘60s, co-founding the Newport Folk Festival in 1959. “We all owe our careers to him,” Joan Baez said. The Kingston Trio's version of Seeger's anti-war song “Where Have All the Flowers Gone?” and Peter, Paul and Mary's take on “If I Had a Hammer” were early ‘60s pop hits. “We Shall Overcome,” a 1948 protest song derived from an old gospel tune, was frequently performed by Seeger during the ‘50s and was adapted by the civil rights movement as an anthem. Now hailed as an avatar of the protest song, Seeger was to return to network television in 1967 to perform on “The Smothers Brothers Comedy Hour,” only to be cut from the broadcast when his anti-war song “Waist Deep in the Big Muddy” proved too much for network executives. He finally performed the song on the show in February 1968 when the Smothers Brothers complained about the censorship.

Seeger's unwavering commitment to righteous protest in the name of working people, his opposition to wars in Vietnam and Iraq, and his deep commitment to environmental causes earned him the respect of not only musicians, but of the same federal government that once gave him such a hard time. Seeger was awarded the National Medal of Arts and honored at the Kennedy Center in 1994. He performed with Springsteen at President Barack Obama's 2009 inauguration, and President Bill Clinton once called him “an inconvenient artist who dared to sing things as he saw them.”

Yet Seeger often deflected attention from himself, and threw it back on his audience. Nothing delighted him more than to see people singing along and enjoying themselves, or picking up instruments and writing their own melodies. He was, in the words of Studs Terkel, “America's tuning fork,” an instrument for measuring the tenor of the times. His repertoire of originals and traditionals proved endlessly mutable. The songs he popularized were adapted in subsequent decades by singers, from the folk vernacular and otherwise, to address current events. Perhaps the most radical aspect of Seeger's life was that he could not be pinned down to an era. His ideas and songs remain everywhere. As Springsteen wrote in the liner notes to his 2006 album “The Seeger Sessions”: “Street corner music, parlor music, tavern music, wilderness music, circus music, church music, gutter music, it was all there waiting in these songs.”

Two suburban men assaulted and robbed a panhandler on the South Side on Monday—then came back and beat him again after one of the men left his cellphone at the scene, prosecutors said at a court hearing Tuesday.

A day after Trevor Noah was declared the new host of "The Daily Show," his graphic tweets targeting women and Jews are causing a social media backlash and Comedy Central is defending its newest late-night star.